DESCRIPTION: (Applicant's Abstract) Studies on the effects of prenatal exposure to psychomotor stimulants on developing monoaminergic neurons are limited by a number of experimental variables including dosage, dosage regimen, gestational age, duration of exposure and postnatal age at which the progeny are examined. Given these complexities, studies on this issue have been few in number despite the general awareness of the severe public health problem of exposure of the fetus to agents with neurotoxic potential. Prenatal drug exposure is known to result in neurologic, cognitive and behavioral deficits in the developing human which can affect the mental health of such individuals throughout their life history. In order to simplify the experimental demands of such studies, we propose to utilize the three-dimensional reaggregate tissue culture system, which we have shown provides an appropriate screen for effects of in utero drug exposure in the intact brain, as a means of `pin-pointing' critical doses and exposure times for design of in vivo experiments. This culture system provides a method for the in vitro reconstruction and development of specific neuronal projections with circuitry similar to that in the intact brain. The reaggregates, formed from disassociated embryonic cells, contain intact, functioning and interacting monoaminergic neurons which develop and respond to pharmacological and toxicological agents in a manner remarkably similar to that observed in vivo. It has been possible to maintain such reconstructed neuronal projections for extended periods of time, up to one year, permitting one to monitor drug-induced effects during the entire developmental history of neurons from the fetal to the adult stage. Specifically, we intend to monitor dopaminergic and serotonergic function by measuring neurotransmitter release as well as monoamine tissue levels over time in culture following in utero exposure of such neurons to a commonly used psychomotor stimulant, methamphetamine. The results of such in vitro studies will be used to design experiments to verify and extend these findings in vivo. Direct comparison of methamphetamine-induced alterations in monoaminergic function in vitro and in vivo have already demonstrated the validity of this approach. In addition, the reaggregate issue culture system will be used to determine whether in utero exposure to methamphetamine results in increased vulnerability of monoaminergic neurons to the neurotoxic effects of common therapeutic agents such as methylphenidate, used in the treatment of children with Attention Deficit Disorder, fenfluramine, an appetite suppressant, or methamphetamine, a commonly used psychomotor stimulant. The objectives of this proposal are to provide a practical approach to the assessment of neurotoxicological risk to the fetus of psychomotor stimulants used by pregnant females in early and mid-gestation.